The fountain of youth may simply be a healthy diet and reduced stress after all, not a magic pill or expensive cosmetics.

Comprehensive lifestyle changes, including more fruit and vegetables as well as meditation and yoga, were shown to reverse signs of ageing at the cellular level for the first time in a study published today.

Adopting a diet rich in unprocessed foods combined with moderate exercise and stress management over five years increased the length of telomeres, the ends of chromosomes linked to ageing, according to a study of 35 men published in the Lancet medical journal. No previous study has shown the effect of lifestyle changes on telomere length, the authors said.

The research, led by Prof Dean Ornish, founder of the Preventive Medicine Research Institute, adds to evidence of the benefits of healthy habits.

“So often, people think it has to be a new drug or laser, something really high-tech and expensive, to be powerful,” said Prof Ornish. “Our studies are showing that simple changes in our lifestyle have powerful impacts in ways that we can measure.”

Prof Ornish collaborated on the study with Elizabeth Blackburn, who shared the Nobel Prize in medicine in 2009 with Carol Greider and Jack Szostak for research on the telomerase “immortality enzyme,” which prevents telomeres from being shaved off.

He was inspired by Blackburn’s research showing that the shortening of telomeres, and therefore ageing, is accelerated by emotional stress such as that experienced by women who have parents with Alzheimer’s disease or children with autism.

The study included 35 men with low-risk prostate cancer enrolled between 2003 and 2007. Ten men adopted the lifestyle changes, while 25 underwent active surveillance as a control group.

The diet encouraged in the lifestyle change group was largely a whole foods, plant-based regimen of fruit, vegetables, whole grains and legumes, with few refined carbohydrates, Ornish said. It wasn’t strictly vegetarian or vegan.

In addition to changes in diet, the program included 30 minutes of walking six days a week; 60 minutes of daily stress management, mostly in the form of yoga and meditation; and a 60- minute support group session once a week.

Telomere length increased among the men in the lifestyle intervention group and decreased in the control group. As telomeres become shorter, cells age and die more quickly. The study authors said they are “rather like the tips of shoelaces that keep them from fraying.”

The study is limited by the small size and by the fact that it wasn’t randomised, which increases the possibility of unknown sources of bias, the authors said. The results suggest larger randomised studies in different populations would be useful, they said.

Prof Ornish is the author of six best-selling books, including Dr Dean Ornish’s Program for Reversing Heart Disease; Eat More, Weigh Less; and The Spectrum.